This invention relates to chloralin (4-chloro-3,5 dinitrobenzotrifluoride) and related compounds for use against parasites having microtubules, including Gardia, Plasmodium, Trypanosome and Leishmania parasites.
Leishmaniasis is a disease that presents a major public health problem worldwide, with approximately 12 million to 40 million persons estimated to be infected. Previously the treatment of choice has been pentavalent antimony in the form of sodium stribogluconate or megluminic antimonate. Both agents are administered intravenously and produce severe adverse side effects. Hospitalization of the patient during treatment is required. Clinical failures are not uncommon. Drugs that are more easily administered and are less toxic are required.
Microtubule inhibitors have been exploited previously as antihelminthic drugs, in cancer therapy and as herbicides. Trifluralin, a microtubule inhibiting herbicide, has been shown to inhibit Leishmania species. The mechanism of action of these microtubule inhibitors in plants has been studied. Dinitroaniline herbicides such as oryzalin and trifluralin interact directly with the major microtubule protein, tubulin, leading to disruption of mitosis.
Although antimicrobial dinitroaniline herbicides show great potential as antiprotozoal compounds, disputed indications of potential carcinogenicity will probably keep trifluralin from being developed for human use.
It is the purpose of this invention to provide improved means for treating infections caused by organisms that have microtubules by administration of 4-chloro-3, 6-dinitrobenzotrifluoride and related compounds which may be administered at a dosage sufficient to attain a blood concentration of 0.5 xcexcM to 500 xcexcM.
Materials and Methods
3-chloro-3,5-dinitrobenzotrifluoride (compound 1), 4-chloro-3-nitrobenzotrifluoride (compound 4), 3-amino-4-chlorobenzotrifluoride (compound 5), 2-bromo-3,5(bis(trifluoromethyl)aniline (compound 6), 4-methoxy-3-nitrobenzotrifluoride (compound 7), and 2-nitro-4-(trifluoromethyl)thiophenol (compound 8) were obtained from Aldrich Chemical Company and were used to without further purification. Trifluralin was obtained from Reidel de Haen and was used without further purification. 4-chloro-3-nitro-5-sulfonylbenzotrifluoride (compound 2) and 4-chloro-3-nitro-5-carboxybenzotrifluoride (compound 3) were obtained from the Walter Reed Army Institute of Research inventory and were used without further purification. All of the agents were initially dissolved in dimethyl sulfoxide and were then diluted at 100 fold in parasitic culture medium before being tested against Leishmania species.
Of the seven compounds tested, the chloralin and compounds 2, 4, and 8 were found to be much more effective than trifluralin.
A comparison of the antiparasitic activities of analogues with electron withdrawing groups of different strengths but the same leaving group Cl, showed a correlation between the strength of the electron-withdrawing group and the activity of the compound against Leishmania promastigotes.
Compounds of the invention are of the formula: 
wherein R4 is a leaving group such as chloro, alkoxy, bromo, an amino which forms a primary or secondary amine, hydroxy or thiol; R3 and R5 are H, nitro, amino, CF3, carboxy or sulfonyl group, wherein at least one of R3 and R5 is nitro. The compounds, when tested, showed the following concentrations to be effective at the IC50 level:
Of particular value are the compounds wherein R4 is chloro and R5 and R3 are nitro or a sulfur containing substituent such as sulfonyl.
The active agents may be administered systemically to attain the effective blood concentration of 0.5 xcexcM to 500 xcexcM concentration in the blood. For example, the active agents may be administered orally, intramuscularly or, in the case of a severely ill patient, intravenously, in appropriate pharmaceutical carrier. Additionally, for cutaneous infections, the active agents may, for example, be administered as salves, ointments, gels, or lotions to the affected areas. Furthermore, the compounds, when given with transdermal carriers, may be administered dermally for systemic effect.
Compositions for administration are exemplified. However, such examples should not be viewed as limiting the invention.